1. Technical Field
The present invention relates to a charging device, an imaging cartridge and an image forming apparatus having the charging device.
2. Description of Related Art
Recently, image forming apparatuses have been miniaturized for cost reduction and further speed increases and higher resolutions have been requested.
In order to realize miniaturization of the apparatus, a charging method has been adopted which places a curvature surface to face an outer circumferential surface of a photoconductive drum using a grid having the curvature surface in a charging device, charges the photoconductive drum, and improves charging characteristics. In the charging method using the grid having the curvature surface, the distance between the outer circumferential surface of the photoconductive drum and the grid curvature surface affects charging efficiency.
As a technique for improving the charging efficiency, as described in Unexamined Japanese Patent Publication No. 2008-298876, there is a technique which provides a gap roller carrying the photoconductive drum in the charging device, and relatively adjusts the distance between the photoconductive drum and the grid by changing the height of the gap roller.
However, although the charging efficiency can be improved by the technique of the related art mentioned above to some extent, it is impossible to improve the charging efficiency to a degree capable of higher resolutions, higher speeds and further miniaturization that can be required for the apparatus for the future.